BOULDER, Colo. — Ground controllers successfully fired the thrusters on NASA’s Mars Reconnaissance Orbiter (MRO) Aug. 30, bringing an end to a six-month-long aerobraking maneuver and placing the spacecraft one step closer to being able to use its entire suite of science instruments.
Launched in August 2005, MRO swung into an elongated orbit around Mars in March when it began dipping in and out of the Martian atmosphere, using the resulting friction to adjust its orbit. This technique, known as aerobraking, eliminates the need for the spacecraft to be launched with the large amount of fuel that would otherwise be required place it in the proper orbit for its mission.
The decision to end aerobraking maneuvers was made early Aug. 30 , said James Graf, MRO project manager at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif. Firing its thrusters got MRO out of the Martian atmosphere. After the completion of two additional maneuvers scheduled to take place over the next two weeks, the spacecraft should enter its science-gathering orbit, Graf said.
“I am greatly relieved that the aerobraking phase is over,” Graf said. “All of aerobraking, but in particular the last demanding week, is dangerous and it is great to have it behind us.”
Graf saluted a combined JPL and Lockheed Martin Space Systems team that “performed fabulously over the last six months — as did the spacecraft.” With the aerobraking behind MRO operators, he said, the spacecraft team is moving onto the commissioning of MRO’s instruments.
The $750 million MRO mission is designed to contribute to several science objectives: determine whether life ever arose on Mars; characterize the climate and geology of Mars; as well as prepare for eventual human exploration of the red planet.
This upcoming phase has its own set of challenges, Graf said. Those include the deployment of the Shallow Subsurface Radar antenna and the lid for the Compact Reconnaissance Imaging Spectrometers for Mars, he said.
“The engineering images returned from these instruments at the end of the month should be astounding,” Graf predicted.
Wayne Sidney, MRO Flight Engineering Team Lead for Lockheed Martin Space Systems, the firm that designed and built the spacecraft in neighboring Denver, said regular MRO burns over the last six months were on the order of seconds. The Aug. 30 burn, by contrast, lasted several minutes, he said, adding that it was “the biggest burn” conducted with just the spacecraft’s Trajectory Correction Maneuver thrusters.
The burn was executed on time and performance was perfect, Sidney said. “The spacecraft is in great shape. Aerobraking is now officially over.”
There’s still more nudging to do with MRO over the next few months, fine-tuning tweaks that push the probe into its final, desired orbit. The mission’s main science observations are scheduled to begin in November, after a period when there will be only intermittent communications with the spacecraft while Mars passes nearly behind the Sun.
Overall, MRO is in excellent health, Sidney said . However, one nagging item cropped up a few weeks ago. A radio frequency switch that allows controllers to flip between MRO’s high- and low-gain antennas is stuck. A team of experts is investigating the issue, trying to ascertain the root, probable cause of the problem.
“If we don’t get the switch unstuck we’ve lost some redundancy…but we still have the capability to communicate over the low- and high-gain antennas using the other transmitter,” Sidney said .
Dipping in and out of the martian atmosphere, MRO saw very few surprises. A worry for aerobraking specialists is encountering dust storm activity that can mix things up in the atmosphere, playing havoc with the delicate, spacecraft-slowing maneuvers.
“The atmosphere has been very cold and clear the whole six months as we hoped it would be,” Sidney said.
